QBus termination?

From: Paul Koning <pkoning_at_equallogic.com>
Date: Tue Feb 8 14:45:24 2005

>>>>> "Vintage" == Vintage Computer Festival <vcf_at_siconic.com> writes:

 Vintage> On Tue, 8 Feb 2005, Eric Smith wrote:
>> Sellam wrote: > Duh, what I meant is that the M9400-YA is in a
>> second bus segment. So > does the bootstrap on there not conflict
>> with the bootstrap on the DSD > controller because they are in
>> different segments?
>>
>> Only if the bus segments aren't connected together.

 Vintage> In this case, the two board Emulex tape controller is
 Vintage> between the two bus segments: one board is in the last slot
 Vintage> of the first segment and the other board is in the first
 Vintage> slot of the second segment. They are connected by a ribbon
 Vintage> cable.

It isn't really clear, but it doesn't sound like these "segments" are
different transmission lines. If you were dealing with bus repeaters
(as found on large Unibus configurations) then yes, you have two
separate transmission lines, one one each side of the repeater. And
sure enough, a Unibus repeater has terminators (one on each side).

If these "segments" you're talking about are just bits of backplane
connected by bus cable, then for transmission line purposes the whole
collection is a single transmission line, and you'd want one
terminator at each end of the whole thing -- and nowhere else.

Also, as was pointed out, for sufficiently small configs you can omit
a terminator safely, but it would be a bad idea to try doing that if
you have multiple pieces connected by cable.

    paul
Received on Tue Feb 08 2005 - 14:45:24 GMT